IDH1 and central nervous system cancer: Choline is increased in many tumors due to increased cell membrane synthesis and increased cellularity, which in IDH-mutant gliomas may be due to mutant IDH-mediated cellular proliferation.21 Gliomas may also demonstrate decreased creatine peak at 3.03 ppm, which sums contributions from creatine and phosphocreatine, GABA, lysine, and glutathione.